Various adjustable attachments are known for securing the axle of the rear wheels of a wheelchair and some of these provide incremental adjustments. However, these incremental adjustments are found to be insufficient for locating the rear wheel at a precise location for the need of the intended occupant. Because the loads of a wheelchair are transmitted to its seat by the rear wheel through the rear axle and its attachment, it is important to assure that these attachments are rigid and well secured to the frame of the wheel chair as it is subjected to stresses exerted on different axes. In U.S. Pat. Nos. 5,284,350, 4,477,098 and 5,060,962, the mounting plates for the rear axle are mounted horizontally and these have proven problematic in view of the different angular loads transmitted thereto through the rear wheel axle. It is also important to construct these mounting plates to provide maximum rigidity and infinite adjustments in both the x and y axes whilst maintaining the mounting attachments as light as possible. It is also desirable that the rear axle mounting assembly can be adapted for wheel chairs which are also collapsible.
The positioning of the rear wheel axle of a wheelchair on its center of gravity is directly proportional to the performance of the wheel chair. A center of gravity that is too much to the rear of the wheelchair provides more resistance on the rear wheels which need to be displaced by the user person. A center of gravity that is too forward provides for a very unstable wheel chair. Accordingly, it is important to provide for a rear axle support assembly which provides infinite adjustments to precisely position the rear wheel axis on its center of gravity taking in consideration the intended user. The effort of propulsing the rear wheels of a wheelchair is proportional to the position of the rear wheel axis and a perfectly adjusted position will considerably reduce the efforts necessary to propulse the wheelchair by diminishing the propulsion effort exerted by the user person. Such precisely disposed rear wheel axis will reduce the fatigue of the user person and in long term greatly retard the wear of the articulations of the user person.
Wheelchair armrests are also essential elements for the comfort of a user person. As well as being an element which is aesthetically pleasing it also is important that the armrest be strong, functional and ergonomic. Such armrests must also protect the clothing of the user, that is to say it must be designed such that the clothing of the user person not be tangled in the armrest or damaged or soiled thereby. It should prevent the clothing of the user person from being tangled up in the rear wheels during movement of the wheelchair. There are two principle utilizations of a wheelchair armrest and that of resting the arms of the user when the wheelchair is at rest and also permits the user person as a rigid grasping member in order to disembark from the wheelchair or move itself on the seat when uncomfortable. A person may access its wheelchair and disembark it several times during a day and therefore this armrest must also be rigid due to the forces applied thereto by the user person. Several types of armrests are known for a wheelchair and U.S. Pat. Nos. 4,768,797, 3,993,351, and 5,255,956 are examples of these. Several armrest designs are also known for office chairs, particularly those intended for persons using a computer and being seated thereon for long periods of time. Concerning wheelchair armrests, some of these are adjustable in height by the use of a slide bar support, thus providing a “T”-shaped structure. Another type of armrest, particularly for office chairs, is one that is pivotally mounted at a rear end whereby to pivot upwardly and rearwards and these are secured on a fixed pivot pin usually to the backrest of the armchair or the rear of the seat thereof.